The GABA(A) receptor 3 subunit gene GABRB3 has been strongly implicated in the pervasive developmental disorders (PDD). GABRB3 lies within chromosome 15q11-13, and anomalies in this region are associated with Rett syndrome, Prader-Willi syndrome, Angelman Syndrome, and are the single most frequent cytogenetic abnormality found in the autism spectrum disorders (ASD). It has recently been recognized that peripheral GABA(A) receptors are involved in immune cell regulation and that activation of GABA(A) receptors can attenuate tissue inflammation. Maternal inflammation during pregnancy has been an environmental factor associated with ASD and we have found that loss of one GABRB3 allele in mother and fetus is sufficient to markedly increase placental pathology in response to cytokines produced by a mild maternal innate immune response in mice. In contrast, activating GABA(A) receptors during a maternal immune event attenuates the impact to the fetus. This implicates GABA(A)-related immune alterations and placental vulnerability as a potential gene-environment interaction which is associated with increased risk of ASD and other PDDs. Importantly, the maternal inheritance pattern of 15q11-13 anomalies suggests that GABA(A)-related immune functions may be altered in mother, as well as in the placenta and fetus. The experiments proposed here test whether selective loss of GABARB3 in the mother, placenta or fetus increase the risk of developing autistic features in offspring following a prenatl maternal immune event.